High frequency electron discharge device



0. HQEIL' March 18, 194-1.

HIGH FREQUENCY ELECTRON DISCHARGE DEVICE Original Filed Feb. 23, 1935 2Sheets-Sheet l INVENTOR Oskar H eLL 0. HEIL March 18, 1941.

HIGH FREQUENCY ELECTRON DISCHARGE DEVICE 2 Sheets-Sheet 2 Original FiledFeb. 23, 1935 Fig. 7.

Patented Mar. 18, 1941 UNITED STATES PATENT OFFICE 2,235,497 menFREQUENCY ELECTRON mscnsnen navron hell, Indwifen-on-the-Rhine, Germany,ignor to o Corporation of America, New York, N. 2., a corporation ofDelaware ary 23, 1934 paratusfor producing short electromagnetic waves.

Asis well known, undamped short electromagnetic waves are producedeitherby the back coupling method utilized in connection with long waves, orby an arrangement utilizing oscillating electrons, for example asproposed by Barkhausen and Kurz, or by means or an arrangelo mentutilizingrevolving electrons, suchas the magnetron.

The present invention is based on an entirely novel principle of short.wave generation, and neither back coupling, nor revolving electrons areutilized therein.

In 'order that the invention may be well understood, a few fundamentaldefinitions will be first of all referred to.

The Faraday cage is a hollow metal body. It

has the property that an electric charge located e in its interiorhas'the same relation towards the exterior, as if it were located on themetal. Therefore, an electron located in the hollow a 'space of theFaraday cage has the same eiiect outwardly asif ithad settled on themetal itself,

and hence movement of an electron within the cage has no effect on thecage and changing voltage on the cage has no eiiecton an electron withinthe cage since the interior of the cage is a field free space.

It is furthermore known that an electron in flight approaching aconductor or receding there from represents an electric current away froor towards said conductor.

. The invention will now be explained, remem- 3 to 4 no observation canbe made outside. The

effect is the same as if the electron had settled on the metal of thecage. when, however, the

electron leaves the Faraday cage at 4 there will be a sudden current inthe opposite direction, since the electron is now receding. It islmderstood of course that a circuit is connected between the cage 2 andcathode 5 and collector 6, and that proper voltage sources are connected55 between cathode 5, electrode 2 and collector 6 "period of dwell,"

. t (c 250-2i.5) This invention relates to a method of and apto makeelectrons move from cathode 5 to collector 5.

In the whole of these considerations the most important factor is thetime during which the electron moves in the cage. For brevity this 8period of time will hereinafter be referred to as The length of theperiod of dwell is proportional to the distance 3-4 and inverselyproportional to the velocity of the electron. If the distance 3-4 is afixed one, the 10 period of dwell or transit time of the electronthrough the hollow electrode depends solely upon the velocity of theelectron. If the Faraday cage is caused to be strongly positive ascompared to the electron emitting cathode 5, then electrons 1B of greatvelocity will fly therethrough and the period of dwell will be veryshort. If the Faraday cageis caused to be only slightly positive ascompared to the cathode, then slow moving electrons will flytherethrough-and the period of 80 dwell will be very long. If a veryrapidly alternating potential is applied to the Faraday cage in the formof oscillations of very high frequency,

then the period of dwell will depend upon the potential to which theFaraday cage is raised at the instant the electron enters. While theperiod of dwell elapsesthe potential of the Faraday cage is altered, sothat when the electron emerges therefrom the cage will be at a diffeerntpoten- 3 tial.

The most important fact which may be deduced from the precedingconsiderations is as follows: Electrons entering the Faraday cage duringthe negative half period are slow and will not leave the cage until thefollowing positive half period. 35 Electrons entering the Faraday cageduring the positive half period are fast and will mostly leave the cageduring the same half period. More specifically if an unmodulated streamof electrons is directed through the hollow elec- 40 trode and assumingan alternating voltage is applied to the electrode, the electronsapproaching the electrode will be either accelerated or decel erateddepending upon the voltage at the moment applied to the electrode, thatis, electrons at will be accelerated ii the voltage on the electrode isbeginning or is in its positive half cycle or will be decelerated if thevoltage is beginning or is in its negative half cycle. with any hollowelectrode, since the space within the electrode is all at the samepotential, that is is a field free space, the speed of the individualelectrons .through the electrode will be that which the individualelectrons have upon entering the hollow electrode, that is, theaccelerated electrons will continue to move rapidly at a constant speedthrough the electrode and the decelerated electrons at a. slow constantspeed through the tubularelectrode. The result is that the fastelectrons overtake the slow electrons causing a resulting change in thedensity of different portions of the electron beam, with a dense cloudof electrons separated by sections where the electrons are few. Theextent to which this action takes place is determined by the length ofthe tube and the transit time or speed of the electrons. This spacewithin the hollow electrode may thus be considered a space where theelectrons drift to form the dense and rarefied portions of the beam andthe result is a density modulation of the electron stream.

Considering now the electron balance ofv the Faraday cage the resultobtained is asfollows: In the negative half period the ingress ofelectrons is predominant. In the positive half period the egress ofelectrons is predominant. But a negative body becomes more negative bythe inress of electrons and a ,positive body becomes erator.

Further and in more detail, as the electrons leave the hollow electrode,depending upon the cycle of the applied voltage, .the electrons willeither give up or take away energy from the electrode. If the electronsleave during the positive portion of a cycle, they are slowed down andgive up energy to the electrode, thus producing an inductive outputeffect and inducing a voltage in the electrode. On the other hand, ifthe electrons leave during the negative portion of the cycle, they areaccelerated and absorb energy from the electrode. Normally this hollowelectrode when incorporated within a tube of the kind underconsideration has such length and the voltages applied are such thatthere is a net transfer of, energy from the electrons to the electrode,which if applied to an oscillating circuit' connected to the electrodemay be used to furnish the modulating voltage to the electrode. On theother hand, if. the electrons are first modulated before being directedthrough the tube, the electrode can be used as an inductive outputelectrode. The frequency at which the electron stream is modulated, thenatural period of frequency of oscillation of the tubular electrode andits associated circuit, and the transit time of the electrons may be soadjusted that the oscillating circuit will receive energy from themodulated electron stream.

It will be apparent from the foregoing that according to this inventionapparatus for producing short electromagnetic waves comprises, in

an electron discharge tube, hollow metal bodies adapted to formelectrically oscillating electrodes and caused to perform suchoscillation by electrons flying therethrough'.

.Some details will now be described which apment of the invention.

In the production of very short waves the flight of the electrons to thehollow metal body and the flight of the electrons away therefrom must bevery rapid. This maybe achieved by disposing between the cathode and thehollow metal body. or hollow metal body and the anode a stronglypositive grid (accelerating electrode), or by disposing a positive gridaround the hollow body.

Preferably, the electrons are caused toform a pencil or beam byproviding a negative electrode surrounding the cathode after the mannerof a Wehnelt cylinder. This makes it possible to utilize smaller hollowmetal bodies and the capacity of same will be small.

The said negative electrode or a control 'grid may be utilized tocontrol theflow of the electrons. 4 This will enable the-waves to begenerated to be conveniently modulated by an oscillating circuitconnected between the cathode and control grid.

A double system, with two opposing hollow bodies, may be disposed in asingle electron dis- .charge tube. To these hollow bodies may beconnected Lecher wires or some other oscillating circuit.

The velocity of the electrons which have passed through the hollow metalbody diii'ers. A number of them passes through the hollow bodypractically without loss, a small number of them loses speed. Therefore,if the anode of the electron discharge tube is made strongly positive,all the electrons will reach it. .But they will strong- 1y heat theanode, so that the tube will operate with poor efliciency. If on theother hand, the anode is caused to be only slightly more positivethereby thrown to one side and may be. intercepted by a furtherauxiliary anode. Instead of the slanting anode V-section anodes may beemployed. The said auxiliary anode may-surround the whole systemcylindrically. It picks up all energy losses and, if required may becooled from p outside by water, air or the like, so'that even very largepower tubes become manageable.

The heat generated in the interior of the tube by the impact of veryfast electrons with the hollow body, the positive grid and the anodeplate proved tobe a certain defectof the method de: scribed in theforegoing. To remove this defect it is proposed to provide the hollowmetal body acting as electrically oscillating electrode with ertures forthe. passage of electrons or .rays of electrons, said apertures againcorresponding to.

the section of the rays of electrons. i

The provision of apertures in the hollow metal metal parts.

With a view to concentrating the rays of electrons and to reducingthecapacity between the accelerating electrodes and the hollow metalbodies it is advisable to provide the apertures of the hollow metalbodies .and of the accelerating electrodes with projections. Theseprojectionsmay be in the form of funnels disposed either vertically orat an angle relatively to the said apertures.

In carrying intoeffect the method according to the invention it appearedto be of particular advantage to provide the braking and interceptingelectrodes (anodes) in the form of a plurality of parallel metal platesinsulated one from the other and disposed in the direction of theelectron rays, said plates also having apertures corresponding to thesection of the rays of electrons. The plates are not disposed at rightangles but in a slightly inclined position relatively to-the directionof the electron rays and the potential of successive plates is graduallymore and more negative. As a result, only slow electrons number of theplates employed the smaller will be the'heat generated by the impact ofelectrons.

In carrying into efiect the present method itis of advantage not to'employ a very high vacuum in the electron discharge tubes utilized, sothat narrow pencils of high electron current may be obtained. In thismanner a certain ionic space charge is obtained which compensates andeven over-compensates the space charge due to the electrons.

Because of the high mass of the positive ions their inertia will be sohigh that the ions can be considered stationary as far as the efiects ofhigh frequency fields are, concerned. 'Therefore, the presence of asmall amount of gas will enhance the operation of the high frequencytube by neutralizing the detrimental efiects of the electronic spacecharge.

The nature of the invention will now be explained by reference to theaccompanying drawings, it being understood that it is not'intendedthereby to limit the invention to the specific embodiments illustratedin the drawings. It is obvious that those skilled in the art will beable to devise other embodiments without departing from the spirit ofthe present invention.

Figs. 2, 3 and 4 are diagrammatic cross sectional views of apparatusconstructed according to the invention.

Fig.= 5 is. an elevation of apparatus shown in Fig. 4.

Figs. 6, 7 and 8 are diagrammatical cross sectional views of the hollowmetal body and the accelerating electrode. 1 I

Fig. 9 is a diagrammatic representation of the complete electrodearrangement.

Referring now to Figs. 2 and 3, two plates 8 iorming the negativeelectrode are arranged adjecent to the cathode 5. Said negativeelectrode 8 focuses the electrons emitted by the cathode into twooppositely disposed beams and directs said electrons. The electrons aregiven a very great velocity by the positivegrids I(acceleratingelectrodes) and fly transversely through the hollow metalbodies 2 to the anodes 6, producing oscillations in these metal bodies2.

More specifically the electrons from the cath- 78 ode 5 are formed intobeams by the negatively trodes being indicated at 'I.

and shielding element orgrid I, a hollow induc tive output electrode 2,a second accelerating and shielding element or grid 1 and then collectedby an auxiliary collecting electrode or anode 8. The electrodes may havevarious shapes but in each the. output electrode is shielded from thecathode by the accelerating or shielding electrodeand from the collectorby a second accelerating or shielding electrode. As pointed out above,electrons which approach the hollow tubular electrode 2 during thenegative half cycle are slowed down and leave during the next positivehalf cycle whereas electrons approaching the electrode 2 during apositive half cycle are accelerated and leave the hollow electrodeduring the same half cycle. Thus the velocity of the electrons ismodulated in the space between the first accelerating electrode I andthe hollow tubular electrode 2. After entering the space within thehollow electrode the electrons drift through at the velocity which theyhad on entering the electrode since no field influences their movementthrough the electrode. As a result the fast electrons overtake the slowelectrons within this drift space and leave the tubular electrode 2 inmore or less well defined groups so that portions of the beam are moredense than other portions. This results in a change of density ofdifferent portions of the electron stream. Since the electrons leave theelectrode during the positive half cycle they tend to slow down due tothe positive voltage on the hollow electrode but on doing so give upenergy to the electrode 2 so that any oscillating circuit connectedbetween this electrode'and. the accelerating electrodes I receivesenergy from the decelerated electrons. It is for this reason that thedevice will remain in oscillation and act as an oscillating generator.-

In Fig. 3, in addition to the anodes 6 whic in this case are disposed atan angle relatively to the direction of the rays of electrodes, thereare providedauxiliary anodes 9 (braking and intercepting anodes) whichintercept the slow electrons, that is slow electrons having less energythan the faster electrons are deflected by electrode 6 at low positivepotential to the collector electrode 9 at the higher positive potential.

Fig. 4 illustrates how' the additional anode 9 may be disposed tosurround the whole system in the form of a metal shell.

Fig. 5 also illustrates the connection of the hollow metal bodies actingas ocillating elec-- trodes to the Lecher wires l0.

Figs. 6. 7, 8 and 9 show various possible embodiments'oi the hollowmetal beds and of the accelerating electrodes, the hollow metalbodiesbeing indicated at 2 and the accelerating elec- Tne directed pencils ofelectrons pass through the apertures ll of the hollow metal body and theapertures I! of the accelerating electrodes in the direction of thearrow shown. The hollow metal bodies are preferably cylindrical. butthey may be composed of plane plates, as shown in Figs. 7 and 9. If thepencil or beam of electrons is of point or circular section rather thanrectangular as in the case of a ribbon shaped beam, the said hollowmetal bodies may be structuresmevolutioxiarily symmetrical. to thedirection of the pencil of electrons that is the electrodes 2 maybe-tubular members. The projections of the hollowmetal bodies areindicated at l3, and those of the accelerating electrodes at H. Theprojections may be disposed at right angles or slantingly with respectto the corresponding apertures of the hollow bodies or acceleratingelectrodes.

In Fig. 9 the cathode emitting the electrons is indicated-at 5 and-asshown it is surroundcdby the negative electrode 8 which focuses theelectrons in a pencil or beam and-directs them. The electrons areaccelerated by the positive elec trode I and after passing through thehollow metal body 2 impinge upon the inclined braking or interceptingelectrodes 6. The plate first passed by the electrons is stronglypositive, and each successive plate is less positive than the precedingone. The electrons flying through the apertures of the plates aregradually braked and caused to turn around. The electrons entering at alow speed are caused to turn around sooner, the fast' electrons later,having turned around the electrons are deflected laterally owing to theslanting disposition of the plates and fall on the rear face of theplate through which they have just passed. The path of the electrons isindicated in dotted lines.

In Figure 10 the electron discharge device comprises a cathode 5 andbeam forming electrode 8' adjacent the cathode. The collector electrode6' has positioned between it acceleratingelectrodes 1' and hollowelectrode 2. The elec tronstream from the cathode 5 may be modulated bya control grid 9' positioned between the cathode 5 and the firstaccelerating electrode 1', the modulating signal being applied betweenthe cathode 5' and grid 9' by an input ill. The output H' is connectedas suggested above to the output electrode or hollow electrode 2'. Inthis arrangement the electron beam may be mod-v ulated before it entersthe space between the two accelerating electrodes. This permits the useof the tube as an amplifier as well as an oscillator.

It is obvious that instead of utilizing the electrodes 5 and 8' forforming the pencils oi elec between said accelerating electrodes, andelectron intercepting anodes, said apertures in said hollow metal bodiesand in said accelerating electrodes being of a shape corresponding tothe section of the pencil of electrons, and said electron interceptinganodes comprising a plurality of. parallel plates insulated from oneanother, said plates being disposed at an angle to the direction of thepencil of electrons and having apertures corresponding in shape to thesection of thepencil of electrons, and said apertures in said platesbeing disposed in the direction of the pencil of electrons.

2. An electron discharge tube for producing short, electromagnetic wavescomprising an exhausted envelope, cathode means within said envelope foremitting electrons, anode means within said envelope for interceptingsaid electrons,-

hollow metal bodies each'hav'ing apertures and being connected to a leadwire and disposed be-,

the pathof saidelectrons, and accelerating electrodes provided withapertures mounted between said hollow bodies and said cathode means andsaid anode means respectively.

3, An electron discharge tube for producingshort electromagnetic wavescomprising an exhausted envelope, cathode means within said envelope foremitting electrons, anode means within said envelope for interceptingsaid electrons, negative electrodes adjacent to saidcathode means,hollow metal bodies each having apertures and being connected to a leadwire and disposed between said cathode means and anode means in the pathof said electrons, and accelerating electrodes provided with aperturesmounted between said hollow bodies and said cathode means and said anodemeans respectively.

4. An electron discharge tube for producing short electromagnetic wavescomprising an ex hausted envelope, cathode means within said envelopefor emitting electrons, anode means within said envelope forintercepting said electrons, negative electrodes adjacent to saidcathode means to collect the emitted electrons to form an electron beam,hollow metal bodies each having apertures and being connected to a leadwire and disposed between said cathodemeans and anode means in the pathof said electrons, and accelerating electrodes provided with aperturesmounted between said hollow bodies and said cathode.

said envelope for intercepting said electrons, a

negative electrode adjacent to said cathode to collect the emittedelectrons to form an electron beam, hollow metal bodies each havingapertures,

and being connected to a leadwire and disposed between said cathodemeans and anode means in thepath of said electrons, .and acceleratingelectrodes provided with apertures mounted between said hollow bodiesand said cathode means and said anodemeans respectively, said aperturesin said hollow metal bodies and in said accelerating electrodes being ofa shape corresponding to the cross section of the electron beam.

.7. An electron discharge tube for producing short electromagnetic wavescomprising an ex-- hausted envelope, cathode means within said envelopefor emitting electrons, anode means within said envelope forintercepting said electrons, said anode means being slantingly mountedto the path of the electrons, auxiliary anode means for interceptingelectrons having a low velocity,

negative electrodes adjacent to said cathode. to. collect the emittedelectrons to form an electron beam, hollow metal bodies each havingapertures and being connected to a lead wire and disposed between saidcathode means and anode means in the path of ,saidelectrons, andaccelerating electrodes each provided with an aperture mounted betweensaid hollow bodies and said. cathode-- means and said anode meansrespectively, said apertures in said hollow metal bodies and in saidaccelerating electrodes being of a shape corresponding to the crosssection of the electron aperture in said anode, and brealnng andintercepting electrodes beyond said anode comprising a plurality ofparallel insulated plates each having an aperture and mounted with saidapertures? aligned with the aperture in said anode to be in the path ofsaid electron beam, said plates being inclined to the path of said beambeyond said anode.

9. A short wave electron discharge tube comprising anevacuatedenvelopeenclosing means including an electron emitting cathode forforming an electron discharge fromsaid cathode into an electron beam,electron intercepting electrodes comprising a plurality of insulatedmetal plates inclined to the direction of and mounted to intercept theelectron beam, spaced accelerating electrodes between said means andsaid intercepting electrodes'and having aligned apertures in the path ofthe electron beam, a hollow metal body connected to a lead wire anddisposed between and with its ends near said accelerating electrodes andhaving apertures aligned with the apertures of said acceleratingelectrodes, said apertures in said hollow metal body and in saidaccelerating electrodes being of a shape corresponding to thecross-section of the electron beam.

10. A short wave electron discharge tube as defined in claim 9 in whichthe hollow body and the accelerating electrodes have at the aperturestubular projections surrounding the apertures.

11. A short wave electron discharge tube as defined in claim 9 in whichthe intercepting electrodes are parallel and have aperturescorresponding in shape to. the cross-section of the electron beam anddisposed in the path of the electron beam. 7

12. An electron discharge device including an evacuated envelopecontaining a cathode for supplying electrons, means tor forming saidelectrons into a beam; a collector electrode for receiving electrons insaid beam and velocity mod-' ulating means for accelerating anddecelerating said electrons, said velocity modulating means including ahollow tubular conducting member adapted to have alternating potentialsof high frequenciesapplied thereto during operation of I said electrondischarge device and an apertured electrode adjacent each end of saidhollow tubular conducting member and positioned between said hollowtubular conducting member and all for subjecting said beam to a highfrequency field before entering said hollow electrode and after leavingsaid hollow electrode, and a second apertured electrode between saidhollow electrode and said collector electrode. 5 14. An electrondischarge device including an evacuated envelope having a'gaseousatmosphere therein and containing a cathode for supplying electrons.means for iorming said electrons-into a beam, a collector electrode forreceiv ng electrons in said beam and velocity modulating means foraccelerating and decelerating said electrons, said means including ahollow tubular member adapted to have alternating potentials of highfrequency applied thereto during operating of said electron dischargedevice, and an apertured electrode adjacent each end of said hollowelectrode and positioned between said hollow electrode and all of theother "electrodes within said envelope. g

15. A short wave electron discharge device comprisingan evacuatedenvelope enclosing a velocity modulating means comprising a hollow metalI body, means adjacent one end of said-hollow metal body and includingan electron emitting g5 .cathode for forming the electron discharge fromsaid cathode into an electron beam directed through said hollow metalbody, and acollector adjacent the other end of said hollow metal body inthe path or the electron beam which is to be 30 passed through saidhollowlmetal body, and an apertured electrode adjacent each end of thehollow metal body and each having an aperture in the path of theelectron beam through said hollow metal body, said collector beinginclined 35 to-the path of the electron beam through the aperturedelectrodes; 7

16. An electron discharge deviceincluding an evacuated envelopecontaining a cathode for supplying electrons, means for forming saidelec- 4o trons into a beam, a collector electrode for receivingelectrons in said beam and velocity modulating means for acceleratingand decelerating said electrons, said means including a. hollow tubularconducting member adapted to have al- 5 ternating potentials of highfrequency applied thereto during operation of said electron dischargedevice, and an apertured electrode adjacent each end of said hollow.tubular conducting member and positioned between said hollow tubularcon- 80 ducting member and all of the other electrodes within saidenvelope.

17. An electron discharge tube for use at high frequencies including acathode for supplying electrons, means for forming said electrons into65 said electrode means comprisinga hollow body 60 for providing a fieldfree space through which the beam passes after being subjected to saidhigh frequency alternating field, and electrode means between saidcollector electrode and-said. hollow body for abstracting energy fromsaid beam after 08 its passage through the field free space and beforereaching said collector electrode.

18. An electron discharge tube for'use at high frequencies including acathode for supplying electrons, means for forming said electrons into 7c a beam and a collector electrode for said beam, velocity modulatingmeans between said cathode and collector electrode including anapertured electrode and a hollow electrode for applying a high frequencyalternating field to said beam, 78

said hollow electrode providing a'field free space through which thebeam passes after being subjected to said high frequency alternatingfield; and electrodemeans including said hollow electrode and a secondapertured electrode for abstracting energy from said beam after itspassage through the field free space and before reaching said collectorelectrode.

19. An electron discharge tube for use at high 10 frequencies includinga cathode for supplying electrons, means for forming said electrons intoa beam, a collector electrode for said beam, a hollow electrodepositioned between said cathode and collector electrode throughwhichsaid beam is directed, a control electrode between said cathode andhollow electrode for modulating the beam of electrons, an aperturedelectrode positioned between said-control electrode and said hollowelectrode and a second apertured electrode between said hollow electrodeand collector electrode, said hollow electrode and said first aperturedelectrode defining a high frequency field space through which said beamis to-pass before entering said hollow electrode, and said hollowelectrode and said second apertured electrode defining a second highfrequency ,field space through which said beam is to pass after leavingsaid hollow electrode. v

20. An electrondischarge device for producing 30 short electromagneticwaves, including an evacuated envelope, cathode means within saidenvelope for supplying electrons in oppositely disposed beams,anode'means within said envelope for intercepting said beams ofelectrons, a hollow metal body'disposed in each beam path between saidcathode means and said anode means, and accelerating electrodes providedwith apertures mounted between each of said hollow metal bod-q ies andsaid cathode means and said anode.

40 means respectively.

21. A short wave electron discharge tube in cluding an evacuatedenvelope containing a hol-" low metal body, means adjacent one endofsaid hollow metal body and including an electron emitting cathode forforming said electron discharge from said cathode into an electron beamdirected through said hollow metal body, a collector electrodemountedadjacent the other end of said hollow. metal body in the path of the 22.An electron discharge device for use at high frequencies having acathode for supplying electrons, means for forming said electrons into abeam and a collector electrode for said beam, a first aperturedelectrode adjacent said cathode, conductivemeans surrounding theelectron path and located between said first apertured electrode andsaid collector electrode, said conductive means having a surface nextadjacent said first apertured electrode defining therewith a highfrequencyfield space, and a second apertured electrode between saidconductive means and said collector electrode.

23. An electron discharge device for use at high frequencies including acathode for supplying electrons, means for forming said electrons into abeam, and a collector electrode forsaid beam, a pair of aperturedmembers positioned between the cathode and the collector through whichsaid beam of electrons is directed, and a velocity modulating membersurrounding the beam between said apertured electrodes for modulatingthe beam.

' 24. An electron discharge device for use at high frequencies andincluding a, cathode for supplying electrons, means for forming saidelectrons into a beam, and a collector electrode for said beam, a,firstelectrode-meansbetween said cathode and collector electrode forapplying independently of said cathode a high frequency alternatingfield to said beam for velocity modulating the beam,

and a second electrode means between said first electrode means and saidcollector electrode for abstracting energy from said beam after the ap-CERTIFICATE or CORRECTION. Patent No.- 2,25 ,L 97. mar-ch1 [191;1.

- OS KAR HEIL.

It is hereby certified that error appears in the printed specificationof the above nunfbered pater 1t requiring correction as follows Pagel,first column, line 9, for "0i! an" read -of an-- and second column,line'?, for '.'dwell,"' The" read- 'dwell" The -5; line 29, for"'diffeer'nt"-read --different; page}, first COlUJliIl, line 65', after"arrangement" insertthe following paragraph- Figure l0 is a diagrammaticrepresentation of a modification of an electron discharge device madeaccording Y to my invention and its relative 'potentials;

line 65-66, for "a'djecent" rea'd "adjacent"; and second column, line56, for "ocil-lating" readioscillating page 14, first column, line 20,for "later, having" read "later. Having--; and that the said LettersPatent should be read with this correction therein that the same mayconform to the record of the case in the Patent Office. I v

' Signed and sealed this ra day of June, A.- D. 1.9m.

. Henry- Van Am'sdale (Seal) Acting Commi ssi oner of Patent sCERTIFICATE or CORRECTION. Patent No.- 2325 197. march'18, 1'9u1.

- OS KAR HEIL. 4

It is hereby eertified that error appears in the printed specificationof the above numbered patent requirin'g correction as follow s Page 1,first column, line 9, for "or an" read --of anand second column, line 7,for '.'dwell;"- The" read- 'dweil". The-f; line 29, for '"diffeer'nfl-read different--; page}, first column, line 65', after"arrangement? insert the following paragraph I I v Fign re lO is adiagrammatic representation of a modification of an electron dischargedevice made according to my invention and its relative 'po ten tialsline 65-66, for "adjacent" read "adjacent"; and second column, 1ine'56for "ocil'lating" readi osoillating page )4 first-(column, line 20, for"laterQhaving" read -,1a-ter'. Having-; and that'the said-Letters Patentshouldbe read with this correction therein that the same may conform to.the record of the case in the Patent Office.

' signed and sealed this 51-21 day of Jane, A.- D. 1.9!;1.

. Henry- Van Ar'edale (Seal) I Acting Commi ssi oner of Patent s.

